LEDs are widely used in various applications, including indicators, light sensors, traffic lights, broadband data transmission, and illumination applications. Particularly, LEDs attract more interest for illumination applications due to their low power consumption and long lifetime. In illumination applications, LEDs have some limitations, because light emitted from the LEDs is usually distributed in a relatively small angle, which provides a narrow angle of light and is dissimilar to natural illumination or some types of incandescent illuminations.
For example, LEDs are often used in illumination devices provided to replace conventional incandescent light bulbs, such as those used in a typical lamp. These illumination devices require a relatively wide amount of light distribution, similar to that provided by conventional incandescent light bulbs. Therefore, it is desired to provide an LED illumination device that distributes light in a relatively wide angle, similar to that of an incandescent light bulb.